Magnetic Bearings Promise Fewer Trips To the Mechanic

If your auto mechanic charges a king's ransom for car repair, this technology is for you. It's called magnetic bearings. If the technology lives up to expectations, it promises:

*A car that never needs an oil change.

*An engine so light and efficient it gets 80 miles to the gallon.

*An important boost to companies trying to build low-pollution vehicles.

Once used only in costly equipment, magnetic bearings are finding their way into all sorts of applications. Companies and the military are trying them out in jet engines, power plants, even refrigerators. Although more expensive than conventional bearings, magnetic bearings consume less energy, create more power, and require less maintenance. The electronics that control them are getting more affordable.

''We're talking about a potential broad change in the way machines are built,'' says David Eisenhaure, president of SatCon Technology Corporation in Cambridge, Mass.

Just about everyone uses conventional bearings of one kind or another. They're the device that allows one part of a machine to rotate around another part, like a wheel and axle. For example: some wheels turn because little metal balls -- ball bearings -- sit between the wheel and the axle that runs through its center. When the wheel spins, so do the ball bearings, especially if they're coated with grease or some other lubricant.

The new bearings replace the balls and lubricants with an electronically controlled magnetic field. They allow an engine's drive shaft, for example, to ''float'' in the magnetic field. This cuts down friction and wear. It also allows engines to run faster and hotter.

Many industrial motors can't run faster because their conventional bearings get too hot. If the bearings reach a certain temperature, typically 250 degrees F., the lubricant fails and the machine breaks down. Magnetic bearings, which don't use lubricants, could conceivably run at 1,000 degrees. That means an engine could deliver far more power than a conventional engine of the same size and weight.

The technology is still expensive enough that it is mostly going into high-end projects. The Defense Department is experimenting with magnetic bearings as part of its three-year effort to boost turbine-engine performance 30 percent. Commonwealth Edison, a northern Illinois utility, predicts the bearings could be used in power plants to handle peak demand. Chrysler Corporation is putting the technology into a race car, called the Patriot.

The Patriot is an ultra-low-pollution vehicle that its designers hope can reach up to 200 miles per hour. It burns liquefied natural gas and turns it into electricity that powers the car.

Traditional electric cars are heavy because they carry banks of bulky batteries. Using magnetic bearings, the Patriot saves weight in two ways. First, the engine can deliver more horsepower per pound of weight. Second, magnetic bearings allow the Patriot to replace conventional batteries with a flywheel, which is much lighter.

Flywheels store energy the same way a potter's wheel does. (The wheel keeps turning even after the potter stops spinning it.) When the Patriot slows down, its flywheel keeps turning. When the car speeds up, it can draw additional power from the spinning wheel. Of course, the Patriot's flywheel is far more efficient than a potter's wheel. Its magnetic bearings are almost friction-free.

Eventually, this technology could make it into passenger-car engines. Of course, that would mean fewer visits to the auto mechanic.